In situ synthesis of rhodium nanoparticles - Mesoporous carbon hybrid via a novel and facile nanocasting method for simultaneous determination of morphine and buprenorphine.

An in situ and facile nanocasting procedure has been developed to embed Rhodium nanoparticles (RhNPs) in mesoporous carbon (MC) matrix via carbonizing ß-Cyclodextrin capped RhNPs (ß-CDs@RhNPs) as a source of both carbon and metal, in the presence of SBA-15 as hard template. Firstly, ß-CDs was used to coat and stabilize the RhNPs, and then coated RhNPs was applied as carbon source during the carbonization step. In this way, biocompatible materials are used as much as possible. The transmission electron microscopy, field emission scanning electron microscopy, Fourier transform infrared, BET surface area and X-ray diffraction devices were used to characterize the nanomaterials. The nanocomposite (RhNPs-MC) was casted on the glassy carbon electrode (GCE) to fabricate an electrochemical sensor (RhNPs-MC/GCE). This sensor shows high efficiency toward simultaneous determination of Morphine (Mp) and Buprenorphine (Bp), electrochemically, what other modified electrodes cannot do. For Mp, the linear range and limit of detection were obtained 0.1-20 µM and 40 nM, respectively, and these data were obtained about 0.1-14 µM and 45 nM for Bp determination. Less steps of synthesis, biocompatibility and facility are the major advantages of the process, and some benefits of the sensor are its separate signals, fast response time, sensitivity, and simple use without need for pretreatment.

Myoglobin immobilized on mesoporous carbon foam in a hydrogel (selep) dispersant for voltammetric sensing of hydrogen peroxide.

Mesoporous carbon foam (MCF) was prepared by via the Pechini method which is facile and template-free. The MCF was characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and BET surface area analysis. Afterwards, the MCF was dispersed in the natural hydrogel salep to give a composite. Finally, myoglobin was immobilized on the composite and then placed on a glassy carbon electrode (GCE). The modified GCE gives a distinct quasi-reversible redox peak during electroreduction of hydrogen perxide (H2O2). The estimated electron transfer coefficient (α) and the heterogeneous electron transfer rate constant (ks) for redox process of Mb are 0.54 and 2.25 s-1, respectively. The sensor, best operated at -0.2 V (vs. Ag/AgCl), responds to H2O2 in the 1.0 to 80 µM H2O2 concentration range, with a 180 nM limit of detection (at S/N ratio of 3). The technique was applied to the determination of H2O2 in spiked fetal bovine serum samples. Graphical abstract Mesoporous carbon foam (MCF) synthesis, dispersion in Salep solution, preparing the Salep-MCF composite (S-MCF), immobilizing the Mb at S-MCF and preparing Mb/S-MCF composite, Casting the Mb/S-MCF on electrode surface to prepare Mb/S-MCF/GCE and electrochemical behavior of biosensor.

Mesoporous carbon foam, synthesized via modified Pechini method, in a new dispersant of Salep as a novel substrate for electroanalytical determination of epinephrine in the presence of uric acid.

Mesoporous carbon foam (MCF) with particular properties was prepared via a simplistic and template-free procedure. The synthesized MCF was characterized by transmission electron microscopy, field emission scanning electron microscopy, X-ray diffraction and BET surface area techniques. Porous MCF with pores diameters of 5 to 10nm provided a perfect substrate including extensive specific surface area to modify the electrodes surface. The obtained MCF was dispersed in Salep solution to prepare a stable suspension (S-MCF). The resultant composite was casted on the surface of glassy carbon electrode (GCE) to assemble the S-MCF modified GCE (S-MCF/GCE). Cyclic voltammetry (CV) was used to study the electrochemical behavior of epinephrine (Ep) and the determination of Ep was conducted by applying differential pulls voltammetry (DPV) in the presence of uric acid (UA). In the optimized conditions, the presented sensor is able to detect the concentration range of 0.1-12µM with a limit of detection of 40nM. The presented methodology possesses a reliable reproducibility, repeatability and stability in biological samples. These results proved that the S-MCF composite has a hopeful capacity in electrochemical sensors development.

A novel and facile synthesis of carbon quantum dots via salep hydrothermal treatment as the silver nanoparticles support: Application to electroanalytical determination of H2O2 in fetal bovine serum.

A simple, low-cost, and green process was used for the synthesis of carbon quantum dots (CQDs) through the hydrothermal treatment of salep as a novel bio-polymeric carbon source in presence of only pure water. The silver nanoparticles (AgNPs) were embedded on the surface of CQDs by ultra-violate (UV) irradiation to the CQDs and silver nitrate mixture solution. The as-synthesized CQDs and AgNPs decorated CQDs nanohybrid (AgNPs/CQDs) were characterized by UV-vis and photoluminescence spectroscopy, Fourier transform-infrared spectroscopy, transmission electron microscopy, atomic force microcopy, X-ray diffraction, and field emission scanning electron microscopy. Then, the AgNPs/CQDs nanohybrid was casted on the glassy carbon electrode in order to prepare an amperometric hydrogen peroxide (H2O2) sensor. The electrochemical investigations show that the AgNPs/CQDs nanohybrid possesses an excellent performance toward the H2O2 reduction. In the optimum condition, the linear range of H2O2 determination was achieved from 0.2 to 27.0µM with high sensitivity (1.5µA/µM) and the limit of detection was obtained about 80nM (S/N=3). Finally, the prepared nanohybrid modified electrode was effectively applied to the H2O2 detection in the disinfected fetal bovine serum samples, and the recovery was obtained about 98%. The achieved results indicate that the AgNPs/CQDs nanohybrid with high reproducibility, repeatability, and stability has a favorable capability in electrochemical sensors improvement.

Differential pulse voltammetric simultaneous determination of acetaminophen and ascorbic acid using single-walled carbon nanotube-modified carbon-ceramic electrode.

Single-walled carbon nanotube-modified carbon-ceramic electrode (SWCNT/CCE) was employed for the simultaneous determination of acetaminophen (APAP) and ascorbic acid (AA). The SWCNT/CCE displayed excellent electrochemical catalytic activities toward APAP and AA oxidation compared with bare CCE. In the differential pulse voltammetry technique, both AA and APAP gave sensitive oxidation peaks at -62 and 302 mV versus saturated calomel electrode, respectively. Under the optimized experimental conditions, APAP and AA gave linear responses over ranges of 0.2 to 150.0 µM (R(2)=0.998) and 5.0 to 700.0 µM (R(2)=0.992), respectively. The lower detection limits were found to be 0.12 µM for APAP and 3.0 µM for AA. The investigated method showed good stability, reproducibility, and repeatability as well as high recovery in pharmaceutical and biological samples.